Heat treatable coated article having titanium nitride and ito based ir reflecting layers

ABSTRACT

Coated articles include two or more functional infrared (IR) reflecting layers optionally sandwiched between at least dielectric layers. The dielectric layers may be of or including silicon nitride or the like. At least one of the IR reflecting layers is of or including titanium nitride (e.g., TiN) and at least another of the IR reflecting layers is of or including indium-tin-oxide (ITO).

This invention relates to coated articles that include two or morefunctional infrared (IR) reflecting layers possibly sandwiched betweenat least dielectric layers, and/or a method of making the same. Inexample embodiments, at least one of the IR reflecting layers is of orincluding titanium nitride (e.g., TiN) and at least another of the IRreflecting layers is of or including indium-tin-oxide (ITO). The coatingmay be designed so that the coated articles realize one or more of:desirable glass side reflective visible coloration that is not too red(e.g., glass side reflective a* color value(s) from −8 to +1.6); adesirably low solar heat gain coefficient (SHGC); desirable visibletransmission (TY or T_(vis)); desirably low film side visiblereflectance; thermal stability upon optional heat treatment (HT) such asthermal tempering; desirably low normal emittance (E_(n)); and/ordesirably high light-to-solar gain ratio (LSG). Such coated articles maybe used in the context of monolithic windows, insulating glass (IG)window units, laminated windows, and/or other suitable applications.

BACKGROUND AND SUMMARY OF THE INVENTION

Low solar factor (SF) and solar heat gain coefficient (SHGC) values aredesired in some applications, particularly in warm weather climates.Solar factor (SF), calculated in accordance with EN standard 410,relates to a ratio between the total energy entering a room or the likethrough a glazing and the incident solar energy. Thus, it will beappreciated that lower SF values are indicative of good solar protectionagainst undesirable heating of rooms or the like protected bywindows/glazings. A low SF value is indicative of a coated article(e.g., IG window unit) that is capable of keeping a room fairly cool insummertime months during hot ambient conditions. Thus, low SF values aresometimes desirable in hot environments. High light-to-solar gain (LSG)values are also desirable. LSG is calculated as T_(vis)/SHGC. The higherthe LSG value, the more visible light that is transmitted and the lessamount of heat that is transmitted by the coated article. While low SFand SHGC values, and high LSG values, are sometimes desirable for coatedarticles such as IG window units and/or monolithic windows, theachievement of such values may come at the expense of sacrificingcoloration and/or reflectivity values. In particular, conventionalattempts to achieve low SHGC values have often resulted in undesirablylow LSG values and/or undesirable visible coloration of the coating. Itis often desirable, but difficult, to achieve a combination ofacceptable visible transmission (TY or T_(vis)), desirable glass sidereflective coloration (e.g., desirable a* and b* glass side reflectivecolor values), low SHGC, desirably low film side visible reflectance,and high LSG for a coated article in window applications, especially ifit desired to use a glass substrate that is not deeply tinted.

SF (G-Factor; EN410-673 2011) and SHGC (NFRC-2001) values are calculatedfrom the full spectrum (T_(vis), Rg and Rf) and are typically measuredwith a spectrophotometer such as a Perkin Elmer 1050. The SFmeasurements are done on monolithic coated glass, and the calculatedvalues can be applied to monolithic, IG and laminated applications.

Silver based low-E (low emissivity) coatings for windows are known inthe art. However, the silver is not particularly durable, and can beeasily corroded if exposed to moisture for instance. Thus, silver basedlow-E coatings are not desirable for monolithic applications such asmonolithic windows, and are typically used in IG window units includingmultiple glass panes, because of the durability problems of silver basedlow-E coatings.

Solar control coatings are known in the art. For example, solar controlcoatings having a layer stack of glass/Si₃N₄/NiCr/Si₃N₄/NiCr/Si₃N₄ areknown in the art, where the NiCr layer may be nitrided. For example, seeU.S. Patent Document 2012/0177899 which is hereby incorporated herein byreference. While layer stacks of U.S. Patent Document 2012/0177899provide reasonable solar control and are overall good coatings, they arelacking in certain respects. The glass side reflective a* values (a*under R_(G)Y) in Examples 1, 4 and 5 in paragraphs 0025-0026 of US '899are −17.8, −15.95, and +2.22, respectively, and the glass side visiblereflectance values (R_(G)Y) in Examples 1 and 4 are 36% and 36.87%,respectively. Examples 1 and 4 in US '899 are undesirable because theglass side visible reflectance (R_(G)Y) values are too high at 36% and36.87%, respectively, and because the glass side reflective a* valuesare too negative at −17.8 and −15.95, respectively. And when R_(G)Y isreduced down to 15.82% in Example 5, this results in the glass sidereflective a* color value in Example 5 becoming too red with a value of+2.22. Thus, the coatings described in US '899 were not able to achievea combination of acceptable visible reflectivity values and glass sidereflective a* coloration values.

Certain known solar control coatings use NbN, NbZr, or NbZrN as IRreflecting layers. For instance, see U.S. Patent Document 2012/0177899and U.S. Pat. No. 8,286,395. However, the instant inventors havesurprisingly found that solar control coatings that use solely thesematerials NbN, NbZr, or NbZrN for IR reflecting layers are lacking interms of normal emissivity (E_(n)) for a given IR reflecting layer(s)thickness. For a given IR reflecting layer(s) thickness, the instantinventors have found that such coatings have undesirably high normalemittance (E_(n)) values, undesirably high SHGC values; and/orundesirably low LSG values.

It would be desirable according to example embodiments of this inventionfor a coating to be designed so as to have a combination of acceptablevisible transmission (TY or T_(vis)), desirable glass side reflectivecoloration (e.g., desirable a* and/or b* reflective color values),desirably low film side visible reflectance, low emittance/emissivity,low SHGC, and high LSG for a coated article in window applications.

In certain example embodiments of this invention, certain applicationssuch as monolithic window applications desire glass side reflectivecoloration that is not significantly red. In other words, certainapplications such as monolithic window applications desire glass sidereflective a* color values that are either negative or no greater than+1.6 or +1.0 (glass side reflective a* values higher than +1.6 areundesirably red). Such reflective a* values are especially desirable forexample in the context of glass side reflective(R_(G[or outside, or exterior])Y) a* values.

Certain embodiments of this invention relate to coated articles thatinclude two or more functional infrared (IR) reflecting layers that maybe sandwiched between at least transparent dielectric layers, and/or amethod of making the same. The dielectric layers may be of or includesilicon nitride or the like. In certain example embodiments, at leastone of the IR reflecting layers is of or including titanium nitride(e.g., TiN) and at least another of the IR reflecting layers is of orincluding indium-tin-oxide (ITO). It has surprisingly and unexpectedlybeen found that the use of these different materials for the differentIR reflecting layers (e.g., as opposed to using TiN for both IRreflecting layers) in a given solar control coating surprisingly resultsin improved optics such as improved glass side reflective a* valuesand/or high LSG values which are often desirable characteristics inwindow applications, and desirably low film side visible reflectance,and the provision of the IR reflecting layer of or including ITO allowscoated articles to be more easily tailored for desired visibletransmission values while the IR reflecting layer of or including TiNcan keep the normal emissivity, SF and/or SHGC values reasonably low.Coating according to embodiments of this invention may be designed sothat before and/or after any optional heat treatment such as thermaltempering the coated articles realize one or more of: desirable glassside reflective visible coloration that is not too red (e.g., reflectivea* color value(s) from −8 to +1.6); a desirably low solar heat gaincoefficient (SHGC); desirable visible transmission (TY or T_(vis));desirably low film side visible reflectance; thermal stability uponoptional heat treatment (HT) such as thermal tempering; desirably lownormal emissivity/emittance (E_(n)); and/or desirably highlight-to-solar gain ratio (LSG). Note that SHGC may be as high as 80%for uncoated glass. The higher the LSG value, the greater the energysaving. Such coated articles may be used in the context of monolithicwindows, insulating glass (IG) window units, laminated windows, and/orother suitable applications.

In an example embodiment of this invention, there is provided a coatedarticle including a coating supported by a glass substrate, the coatingcomprising: a first infrared (IR) reflecting layer comprising ITO on theglass substrate; a first dielectric layer comprising silicon nitride onthe glass substrate over at least the first IR reflecting layercomprising ITO; a second layer IR reflecting layer comprising a nitrideof titanium on the glass substrate over at least the first dielectriclayer comprising silicon nitride, so that the first dielectric layercomprising silicon nitride is located between at least the first IRreflecting layer comprising ITO and the second IR reflecting layercomprising the nitride of titanium; a second dielectric layer comprisingsilicon nitride on the glass substrate over at least the second IRreflecting layer comprising the nitride of titanium; wherein the coatingcontains no IR reflecting layer based on silver; wherein the coating hasa normal emittance (E_(n)) value of no greater than 0.30; and whereinthe coated article has: a visible transmission from about 15-80%, a filmside visible reflectance no greater than 10%, a glass side visiblereflectance no greater than about 30%, a glass side reflective a* valueof from −10.0 to +1.6, and a light-to-solar gain ratio (LSG) of at least1.10.

In an example embodiment of this invention, there is provided a coatedarticle including a coating supported by a glass substrate, the coatingcomprising: a first infrared (IR) reflecting layer comprising ITO on theglass substrate; a first dielectric layer comprising silicon nitride onthe glass substrate over at least the first IR reflecting layercomprising ITO; a second layer IR reflecting layer comprising a nitrideof titanium on the glass substrate over at least the first dielectriclayer comprising silicon nitride, so that the first dielectric layercomprising silicon nitride is located between at least the first IRreflecting layer comprising ITO and the second IR reflecting layercomprising the nitride of titanium; a second dielectric layer comprisingsilicon nitride on the glass substrate over at least the second IRreflecting layer comprising the nitride of titanium; wherein the coatingcontains no IR reflecting layer based on silver; wherein the coating hasa normal emittance (E_(n)) value of no greater than 0.30; and whereinthe coated article has: a visible transmission from about 15-80% and alight-to-solar gain ratio (LSG) of at least 1.15.

In certain example embodiments of this invention, there is provided acoated article including a coating supported by a glass substrate, thecoating comprising: a first infrared (IR) reflecting layer comprisingITO on the glass substrate; a first dielectric layer on the glasssubstrate over and directly contacting the first IR reflecting layercomprising ITO; a second layer IR reflecting layer comprising a metalnitride on the glass substrate over and directly contacting the firstdielectric layer, so that the first dielectric layer is located betweenand directly contacting the first IR reflecting layer comprising ITO andthe second IR reflecting layer comprising the metal nitride; a seconddielectric layer on the glass substrate over and directly contacting thesecond IR reflecting layer comprising the metal nitride; wherein thecoating contains no IR reflecting layer based on silver; and wherein thecoated article has a visible transmission from about 15-80%. In certainexamples, the metal nitride may be a nitride of titanium, zirconium,niobium, or the like. In certain examples, one or more of the dielectriclayers may be of or include silicon nitride.

Thus, this invention covers monolithic window units, IG window units,laminated window units, and any other article including a glasssubstrate having a coating thereon as claimed. Note that monolithicmeasurements may be taken by removing a coated substrate from an IGwindow unit and/or laminated window unit, and then performing monolithicmeasurements. It is also noted that for a given coating the SF and SHGCvalues will be significantly higher for a monolithic window unit thanfor an IG window unit with the same coated article.

IN THE DRAWINGS

FIG. 1 is a partial cross sectional view of a monolithic coated article(heat treated or not heat treated) according to an example embodiment ofthis invention.

DETAILED DESCRIPTION OF CERTAIN EXAMPLE EMBODIMENTS OF THE INVENTION

Referring now more particularly to the accompanying drawings in whichlike reference numerals indicate like parts throughout the severalviews.

A coating 8 is designed so as to have a combination of acceptablevisible transmission (TY or T_(vis)), desirable glass side reflectivecoloration (e.g., desirable a* and b* reflective color values), low filmside visible reflectance, low SHGC, and high LSG for a coated articlefor use in window applications or the like. As visible transmissionincreases when the IR reflecting layer(s) become thinner, parameterssuch as SHGC will also increase, and E_(n) will decrease, with thisbeing based on the desired transmission for instance of a given coatedarticle for a given application. Example applications includearchitectural windows, residential windows, monolithic windows,automotive windows, and/or IG windows.

Certain embodiments of this invention relate to coated articles having acoating 8 on a glass substrate 1, where the coating includes two or morefunctional infrared (IR) reflecting layers 3 and 5 which may besandwiched between at least transparent dielectric layers 2, 4, 6, 7,and/or a method of making the same. Some of the transparent dielectriclayers, such as dielectric layer(s) 2 and/or 7, are optional and neednot be provided in certain example embodiments. The dielectric layers 2,4 and 6 are preferably amorphous, preferably have a k≤0.1, and may be ofor include silicon nitride, silicon oxynitride, zinc stannate, tinoxide, or the like. Transparent dielectric overcoat 7, of or includingzirconium oxide or any other suitable material, is optional. In certainexample embodiments, at least one of the IR reflecting layers is of orincluding titanium nitride (e.g., TiN) and at least another of the IRreflecting layers is of or including ITO. In the FIG. 1 embodiment,upper IR reflecting layer 5 is of or including titanium nitride (e.g.,TiN) and lower IR reflecting layer 3 is of or including ITO. It hassurprisingly and unexpectedly been found that the use of these differentmaterials for the different IR reflecting layers 3 and 5 (e.g., asopposed to using TiN for both IR reflecting layers 3 and 5) in a givensolar control coating surprisingly results in improved optics such asimproved glass side reflective a* values and/or higher LSG values whichare often desirable characteristics in window applications, and theprovision of the IR reflecting 3 layer of or including ITO allows coatedarticles to be more easily tailored for desired visible transmissionvalues and high LSG values while the IR reflecting layer of or includingTiN 5 provides for desirably low normal emissivity and/or SHGC valuesfor a given thickness of IR reflecting material. Coating 8 according toembodiments of this invention may be designed so that before and/orafter any optional heat treatment such as thermal tempering the coatedarticles realize one or more of: desirable glass side reflective visiblecoloration that is not too red (e.g., reflective a* color value(s) from−8 to +1.6); a desirably low solar heat gain coefficient (SHGC);desirable visible transmission (TY or T_(vis)); low film sidereflectance; thermal stability upon optional heat treatment (HT) such asthermal tempering; desirably low E_(n); and/or a desirably highlight-to-solar gain ratio (LSG). In example embodiments of thisinvention, the coating 8 contains no IR reflecting layer based on Ag orAu.

In certain example embodiments of this invention, certain applicationssuch as monolithic window applications desire glass side reflectivecoloration that is not significantly red. In other words, certainapplications such as monolithic window applications desire glass sidereflective a* color values that are either negative or no greater than+1.6 (glass side reflective a* values higher than +1.6 are undesirablyred). Such glass side reflective a* values are not too red and aredesirable in the context of glass side reflective (R_(G)Y) a* values.

Coated articles may optionally be heat treated in certain exampleembodiments of this invention, and are preferably designed to be heattreatable. The terms “heat treatment” and “heat treating” as used hereinmean heating the article to a temperature sufficient to achieve thermaltempering, heat bending, and/or heat strengthening of the glassinclusive article. This definition includes, for example, heating acoated article in an oven or furnace at a temperature of least about 580degrees C., more preferably at least about 600 degrees C., for asufficient period to allow tempering, bending, and/or heatstrengthening. In certain instances, the HT may be for at least about 4or 5 minutes. The coated article may or may not be heat treated indifferent embodiments of this invention. Instead of HT at >600 C (e.g.,tempering), this coating can also achieve desired performance byactivating HT at as low as 350 degrees C. for example. After HT at 350 Cfor example, the glass is not tempered and may be cut to desired size.

FIG. 1 is a cross sectional view of a coated article according to anexample embodiment of this invention. In the FIG. 1 embodiment the solarcontrol coating 8 includes two IR reflecting layers 3 and 5, andtransparent dielectric layers 2, 4, 6 and 7. The coated article includesat least glass substrate 1 (e.g., clear, green, bronze, grey, blue, orblue-green glass substrate from about 1.0 to 12.0 mm thick, morepreferably from 4-8 mm thick, with an example glass substrate thicknessbeing 6 mm), transparent dielectric layers 2, 4, 6 (e.g., of orincluding silicon nitride [e.g., Si₃N₄], silicon oxynitride, siliconzirconium nitride, or some other suitable dielectric), and IR reflectinglayers 3, 5. Upper IR reflecting layer 5 is of or including titaniumnitride (e.g., TiN, preferably a stoichiometric or substantiallystoichiometric type) and lower IR reflecting layer 3 is of or includingconductive ITO. The upper IR reflecting layer 5 is of or includesTiN_(x) in certain example embodiments of this invention, where x ispreferably from 0.8 to 1.2, more preferably from 0.9 to 1.1, with anexample value being about 1.0. These “x” values provide forimproved/lowered emittance values compared to if “x” is too low forinstance. The titanium nitride has been found to be very durablecompared to silver for example, and more resistant to moisture inducedcorrosion compared to silver for example. It has surprisingly andunexpectedly been found that the use of these different materials forthe different IR reflecting layers 3 and 5 (e.g., as opposed to usingTiN for both IR reflecting layers 3 and 5) in a given solar controlcoating provides for surprisingly results as explained herein. While theIR reflecting layer 5 may include some small amount of oxygen in certaininstances, it is preferable that layer 5 is substantially free of oxygensuch as no more than 8% oxygen, more preferably no more than about 5%oxygen, and most preferably no more than about 3% or 2% oxygen incertain embodiments (atomic %). While IR reflecting layer 5 is of orincluding titanium nitride in preferred embodiments of this invention,it is possible for upper IR reflecting layer 5 to be of another metalnitride such as zirconium nitride and/or niobium nitride in alternativeembodiments of this invention. The coated article may optionally includetransparent dielectric overcoat layer 7 of or including a protectivematerial such as zirconium oxide (e.g., ZrO₂) or silicon oxynitride.Optionally, a dielectric layer of or including silicon oxynitride and/orzirconium silicon oxynitride of any suitable stoichiometry may belocated between and contacting layers 6 and 7 in the upper part of thelayer stack in certain example embodiments. In certain exampleembodiments of this invention, coating 8 does not include any metallicIR blocking or reflecting layer of or based on Ag or Au. In certainexample embodiments of this invention, IR reflecting layers 3 and 5reflect at least some IR radiation, and do not contact any other metalor metal based IR reflecting layer. In certain example embodiments, itis possible for each of the layers to include other materials such asdopants. It will be appreciated of course that other layers may also beprovided, or certain layers may be omitted, and different materials maybe used, in certain alternative embodiments of this invention. Forexample, another metal nitride layer 5 could be added above the ITO incertain alternative embodiments of this invention.

The overall coating 8 of FIG. 1 includes at least the illustrated layersin certain example embodiments, with layers 2 and 7 in particular beingoptional. It is noted that the terms “oxide” and “nitride” as usedherein include various stoichiometries. For example, the term siliconnitride (for one or more of layers 2, 4, 6) includes stoichiometricSi₃N₄, as well as non-stoichiometric silicon nitride, and these layersmay be doped with other material(s) such as Al and/or O. The illustratedlayers may be deposited on glass substrate 1 via magnetron sputtering,any other type of sputtering, or via any other suitable technique indifferent embodiments of this invention. It is noted that other layer(s)may be provided in the stack shown in FIG. 1 such as between layers 2and 3, or between layers 3 and 4, or between the substrate 1 and layer2, or the like. Generally, other layer(s) may also be provided in otherlocations of the coating. Thus, while the coating 8 or layers thereofis/are “on” or “supported by” substrate 1 (directly or indirectly),other layer(s) may be provided therebetween. Thus, for example, thelayer system 8 and layers thereof shown in FIG. 1 are considered “on”the substrate 1 even when other layer(s) may be provided therebetween(i.e., the terms “on” and “supported by” as used herein are not limitedto directly contacting). However, there may be the direct contacts shownin FIG. 1 in preferred embodiments.

In certain example embodiments of this invention, dielectric layers 2,4, and 6 may each have an index of refraction “n” of from 1.7 to 2.5 (at550 nm), more preferably from 1.8 to 2.2 in certain embodiments, andmost preferably from about 2.0 to 2.06 in preferred embodiments of thisinvention. One, two, three, or all of these layers 2, 4, 6 may be of orinclude silicon nitride and/or silicon oxynitride in certain exampleembodiments of this invention. In such embodiments of this inventionwhere layers 2, 4, 6 comprise silicon nitride (e.g., Si₃N₄) or siliconoxynitride, sputtering targets including Si employed to form theselayers may or may not be admixed with up to 1-20% (e.g., 8%) by weightaluminum or stainless steel (e.g. SS#316), with about this amount thenappearing in the layers so formed. Even with this amount(s) of aluminumand/or stainless steel, such layers are still considered dielectriclayers. In certain example embodiments, each of the IR reflecting layers3 and 5 is provided between respective nitride layers (e.g., siliconnitride based layers 2, 4, 6) in order to reduce or prevent damage tothe IR reflecting layers during possible heat treatment (e.g., thermaltempering, heat bending, and/or heat strengthening) thereby permittingpredictable coloration to be achieved following the heat treatment atmultiple viewing angles. While FIG. 1 illustrates a coated articleaccording to an embodiment of this invention in monolithic form, coatedarticles according to other embodiments of this invention may compriseIG (insulating glass) window units or the like.

Turning back to the FIG. 1 embodiment, various thicknesses may be usedconsistent with one or more of the needs discussed herein. According tocertain example embodiments of this invention, example thicknesses (inangstroms) and materials for the respective layers of the FIG. 1embodiment on the glass substrate 1 are as follows in certain exampleembodiments for achieving desired transmission, glass side reflectivecoloration, and visible reflectance in combination with a desirably lowSHGC value(s) and/or a desirably high LSG value (layers are listed inorder moving away from the glass substrate 1):

TABLE 1 (Thicknesses in FIG. 1 embodiment) Example Preferred ExampleLayer Range ({acute over (Å)}) (Å) (Å) silicon nitride (layer 2): 20-500{acute over (Å)}  40-200 {acute over (Å)}  50 Å IR reflector (e.g., ITO)(layer 3): 100-1,000 {acute over (Å)}   250-450 {acute over (Å)} 330 Åsilicon nitride (layer 4): 20-1100 {acute over (Å)}   25-400 {acute over(Å)} 300 Å IR reflector (e.g., TiN) (layer 5): 50-450 {acute over (Å)}130-300 {acute over (Å)} 200 Å silicon nitride (layer 6): 20-800 {acuteover (Å)} 300-550 {acute over (Å)} 450 Å overcoat (e.g., ZrO₂) (layer7): 10-150 {acute over (Å)}  20-40 {acute over (Å)}  30 Å

Table 1 above relates to, for example, embodiments where coating 8 isdesigned so that before and/or after any optional heat treatment such asthermal tempering the coated articles realize one, two, three, four,five, six or all seven of: desirable glass side reflective visiblecoloration such as not too red reflective color (e.g., reflective a*color value(s) from −8 to +1.6); a desirably low SHGC; desirable visibletransmission; low film side visible reflectance, thermal stability uponoptional HT such as thermal tempering; desirably low E_(n); and/or adesirably high LSG. In certain example embodiments, lower IR reflectinglayer 5 may be physically thicker than upper IR reflecting layer by atleast 50 angstroms (Å), more preferably by at least 100 Å. In certainexample embodiments of this invention, upper dielectric layer 6 isphysically thicker than center dielectric layer 4 by at least 50angstroms (Å), more preferably by at least 100 Å, and sometimes by atleast 150 Å.

Before and/or after any optional heat treatment (HT) such as thermaltempering, in certain example embodiments of this invention coatedarticles according to the FIG. 1 embodiment have color/opticalcharacteristics as follows in Table 2 (measured monolithically). It isnoted that subscript “G” stands for glass side reflective, subscript “T”stands for transmissive, and subscript “F” stands for film sidereflective. As is known in the art, glass side (G) means when viewedfrom the glass side (as opposed to the layer/film side) of the coatedarticle. Film side (F) means when viewed from the side of the coatedarticle on which the coating is provided. The characteristics below inTable 2 are in accordance with Illuminant C, 2 degree Observer, and areapplicable to HT and non-HT coated articles herein. Glass sidereflective coloration may be such that coated articles appear neutralcolored, blue-green colored, or yellow-green colored in various exampleembodiments of this invention.

TABLE 2 Color/Optical Characteristics (FIG. 1 embodiment monolithic)General Preferred Most Preferred T_(vis) (TY): 15-80% 20-70% 30-60% (or40-60%) a*_(T) −10 to +5 −8 to +2 −6 to 0  b*_(T) −15 to +7 −10 to +3 −9 to 0  R_(G)Y (glass side): ≤30% ≤25% ≤20% a*_(G)   −10 to +1.6   −8to +1.6 −6 to +1 b*_(G) −25 to +9 −9 to +4 −8 to +1 R_(F)Y (film side):≤10%  ≤8%   ≤5% a*_(F)  −9 to +9 −6 to +7 −3 to +5 b*_(F) −14 to +9 −9to +4 −8 to 0  E_(n): ≤0.30 ≤0.25 ≤0.22 SHGC: ≤0.52 ≤0.45 ≤0.42 LSG:≥1.10 ≥1.15 ≥1.22

For purposes of example only, Example 1 representing an exampleembodiments of this invention, as well we Comparative Examples (CE) 1-5,are set forth below.

EXAMPLES

Comparative Examples (CEs) 1-4 and Examples 1-2 were sputter-deposited(as all examples) layer stacks modeled on 4 mm thick clear glasssubstrates. And CE 5 was a layer stacks modeled on 4 mm thick greenglass substrate. The optical measurements are monolithic measurements.Optical data for CEs 1-5 and Examples 1-2 is in accordance withIlluminant C, 2 degree Observer. The silicon nitride layers were dopedwith about 8% Al. The TiN layers were approximately stoichiometric.Layer thicknesses are in angstroms (Å). “L” in Table 4 below stand forLayer (e.g., L2 means layer 2 shown in FIG. 1, L3 means layer 3 shown inFIG. 1, and so forth). It will be shown below that the use of ITO forlayer 3 in Examples 1-2 provided for unexpectedly improved opticscompared to the use of TiN or NiCr for layer 3 in CEs 1-5.

TABLE 3 Layer Stacks of Comparative Examples (CEs) 1-5 Example L2(Si₃N₄)L3(NiCr) or L3(TiN) L4(Si₃N₄) L5(TiN) L6(Si₃N₄) L7(ZrO₂) CE 1: 220 n/a240 670 310 10 40 CE 2: 140 n/a 200 590 240 30 40 CE 3: 40 n/a 180 350120 30 40 CE4: 50 68 n/a 723 268 171 30 CE5: 50 66 n/a 714 261 206 30

Measured monolithically after thermal tempering (HT), the CEs had thefollowing characteristics.

TABLE 4 Measured Monolithic Optical Data (CEs 1-5) Parameter CE 1 CE 2CE 3 CE4 CE5 T_(vis) (TY) (transmission): 18.6% 24.2% 35.3% 23.1% 21.8%L*_(T): 50.2 56.3 66.0 55.2 53.8 a*_(T) −7.2 −7.0 −5.5 −3.15 −5.86b*_(T) −4.3 −1.5 −0.8 −8.27 −7.97 R_(G)Y (glass side refl. %): 9.5% 9.2%13.0% 12.0% 9.6% L*_(G): 36.9 36.4 42.8 41.2 37.1 a*_(G): −3.2 −2.8 −0.3−0.8 −1.45 b*_(G): −3.5 0.4 −5.7 −1.8 −2.1 R_(F)Y (film side refl. %):25.2% 19.1% 10.8% 14.1% 11.2% L*_(F): 57.3 50.8 39.2 44.4 39.9 a*_(F):5.3 4.7 7.0 0.6 −0.3 b*_(F): −8.3 −6.1 −5.4 −4.9 −4.1 E_(n): 0.18 0.250.36 0.25 0.25 SHGC (NFRC-2001): 0.21 0.24 0.31 0.28 0.27 LSG: 0.80 1.011.14 0.83 0.81

Examples 1-2 according to examples of this invention had the followinglayer stack. Layer thicknesses are in angstroms (Å).

TABLE 5 Layer Stack of Examples 1-2 Example L3 (ITO) L4 (Si₃N₄) L5 (TiN)L6 (Si₃N₄) L7 (Si₃N₄) Ex. 1: 330 300 200 450 n/a Ex. 2: 330 20 180 35040

Measured monolithically after HT, Examples 1-2 had the followingcharacteristics.

TABLE 6 Measured Monolithic Optical Data (Examples 1-2) ParameterExample 1 Example 2 T_(vis) (TY) (transmission): 51.97%  54.4% a*_(T)−3.14 −3.2 b*_(T) −2.81 −3.9 R_(G)Y (glass side refl. %): 19.9% 16.0%a*_(G): −4.0 −2.1 h*_(G): −0.9 0.0 R_(F)Y (film side refl. %):  2.2%2.6% a*_(F): +3.35 +5.6 b*_(F): −4.71 +1.8 E_(n): 0.20 0.22 SHGC(NFRC-2001): 0.41 0.42 LSG: 1.25 1.30

An advantage of using ITO and TiNx for the IR reflecting layers, insteadof using TiNx for both IR reflecting layers, is improved thermalperformance such as improved E_(n) and/or LSG value(s). This is shown inthe tables above. It can be seen by comparing CEs 1-5 (Tables 3-4) withExamples 1-2 (Tables 5-6), that the use of ITO in Examples 1-2 (insteadof TiN or NiCr in CEs 1-5) for layer 3 provided for unexpected results.For instance, the LSG values of CEs 1, 4 and 5 were all well less than1.0, which is undesirable. And while the LSG values of CEs 2 and 3 weremore acceptable, but still low, at 1.01 and 1.14, these CEs 2 and 3along with the other CEs had undesirably high film side reflectance of10.8% or higher. And CE3 had an undesirably high normalemittance/emissivity (E_(n)) of 0.36, which means that insufficient IRis blocked by the coating. Thus, for instance, all CEs had undesirablyhigh film side reflectance values, and most had undesirably low LSGvalues. No comparative example (CE) has a sufficiently low normalemittance/emissivity (E_(n)) combined with desirably low film sidevisible reflectance and desirably high LSG.

The use of ITO for layer 3 in Example 1 (instead of TiN or NiCr in CEs1-5) unexpectedly reduced the film side visible reflectance vales tomore acceptable and aesthetically pleasing 2.2% and 2.6% andsurprisingly increased the LSG value to 1.25 and 1.30 which means asignificant energy saving. Moreover, the use of TiN for layer 5 and ITOfor layer 3 allowed normal emittance (E_(n)) to remain in an acceptablerange of no greater than 0.30, more preferably no greater than 0.25, andmost preferably no greater than 0.22.

In an example embodiment of this invention, there is provided a coatedarticle including a coating supported by a glass substrate, the coatingcomprising: a first infrared (IR) reflecting layer comprising ITO on theglass substrate; a first dielectric layer comprising silicon nitride onthe glass substrate over at least the first IR reflecting layercomprising ITO; a second layer IR reflecting layer comprising a nitrideof titanium on the glass substrate over at least the first dielectriclayer comprising silicon nitride, so that the first dielectric layercomprising silicon nitride is located between at least the first IRreflecting layer comprising ITO and the second IR reflecting layercomprising the nitride of titanium; a second dielectric layer comprisingsilicon nitride on the glass substrate over at least the second IRreflecting layer comprising the nitride of titanium; wherein the coatingcontains no IR reflecting layer based on silver; wherein the coating hasa normal emittance (E_(n)) value of no greater than 0.30; and whereinthe coated article has: a visible transmission from about 15-80%, a filmside visible reflectance no greater than 10%, a glass side visiblereflectance no greater than about 30%, a glass side reflective a* valueof from −10.0 to +1.6, and a light-to-solar gain ratio (LSG) of at least1.10.

In the coated article of the immediately preceding paragraph, thecoating in some instances contains only two IR reflecting layers.

In the coated article of any of the preceding two paragraphs, the firstdielectric layer comprising silicon nitride may be located between anddirectly contacting the first and second IR reflecting layers.

In the coated article of any of the preceding three paragraphs, thesecond IR reflecting layer comprising the nitride of titanium maycomprise TiN_(x), where x is from 0.8 to 1.2, more preferably from 0.9to 1.1.

In the coated article of any of the preceding four paragraphs, thesecond IR reflecting layer may contain from 0-8% oxygen (atomic %), morepreferably from 0-5% oxygen (atomic %).

In the coated article of any of the preceding five paragraphs, thecoating may further comprise another dielectric layer comprising siliconnitride or silicon oxynitride located between and contacting the glasssubstrate and the first IR reflecting layer.

In the coated article of any of the preceding six paragraphs, the secondIR reflecting layer may consist essentially of the nitride of titanium.

In the coated article of any of the preceding seven paragraphs, thecoating may further comprise an overcoat comprising an oxide ofzirconium.

In the coated article of any of the preceding eight paragraphs, thecoated article may have a visible transmission from about 20-70% and/ora light-to-solar gain ratio (LSG) of at least 1.15.

In the coated article of any of the preceding nine paragraphs, thecoated article may have a light-to-solar gain ratio (LSG) of at least1.22.

In the coated article of any of the preceding ten paragraphs, the coatedarticle may have a film side visible reflectance no greater than 8%,more preferably no greater than 5%.

In the coated article of any of the preceding eleven paragraphs, theglass substrate may be a clear glass substrate.

In the coated article of any of the preceding twelve paragraphs, thecoated article may have a glass side reflective a* value of from −8 to+1.0, and/or a film side reflective a* value of from −9 to +9.

In the coated article of any of the preceding thirteen paragraphs, oneor more of the dielectric layers comprising silicon nitride may furthercomprise oxygen and/or may be doped with aluminum.

In the coated article of any of the preceding fourteen paragraphs, thecoated article may be a monolithic window.

In the coated article of any of the preceding fifteen paragraphs, thecoated article measured monolithically may have an SHGC value of nogreater than 0.52, more preferably no greater than 0.45, and mostpreferably no greater than 0.42.

In the coated article of any of the preceding sixteen paragraphs, thefirst IR reflecting layer comprising ITO may be from 100-1,000 Å thick,and/or the second IR reflecting layer comprising the nitride of titaniummay be from 50-450 Å thick.

In the coated article of any of the preceding seventeen paragraphs, thefirst IR reflecting layer comprising ITO may be from 250-450 Å thick,and/or the second IR reflecting layer comprising the nitride of titaniummay be from 130-300 Å thick.

In an example embodiment of this invention, there is provided a coatedarticle including a coating supported by a glass substrate, the coatingcomprising: a first infrared (IR) reflecting layer comprising ITO on theglass substrate; a first dielectric layer on the glass substrate overand directly contacting the first IR reflecting layer comprising ITO; asecond layer IR reflecting layer comprising a metal nitride on the glasssubstrate over and directly contacting the first dielectric layer, sothat the first dielectric layer is located between and directlycontacting the first IR reflecting layer comprising ITO and the secondIR reflecting layer comprising the metal nitride; a second dielectriclayer on the glass substrate over and directly contacting the second IRreflecting layer comprising the metal nitride; wherein the coatingcontains no IR reflecting layer based on silver; and wherein the coatedarticle has a visible transmission from about 15-80%.

In the coated article of the immediately preceding paragraph, thecoating may have a normal emittance (E_(n)) value of no greater than0.30, more preferably no greater than 0.25, and most preferably nogreater than 0.22.

In the coated article of any of the preceding two paragraphs, the metalnitride may abe a nitride of titanium.

In the coated article of any of the preceding three paragraphs, thefirst and/or second dielectric layer may comprise silicon nitride.

In the coated article of any of the preceding four paragraphs, thecoated article may have a film side visible reflectance no greater than10%, a glass side visible reflectance no greater than about 30%, a glassside reflective a* value of from −10.0 to +1.6, and a light-to-solargain ratio (LSG) of at least 1.10.

In the coated article of any of the preceding five paragraphs, thesecond IR reflecting layer may contain from 0-8% oxygen (atomic %), morepreferably from 0-5% oxygen (atomic %).

In the coated article of any of the preceding six paragraphs, thecoating may further comprise another dielectric layer which may comprisesilicon nitride and/or silicon oxynitride located between and contactingthe glass substrate and the first IR reflecting layer.

In the coated article of any of the preceding seven paragraphs, thecoating may further comprise an overcoat comprising an oxide ofzirconium.

In the coated article of any of the preceding eight paragraphs, thecoated article may have a visible transmission from about 20-70% and/ora light-to-solar gain ratio (LSG) of at least 1.15.

In the coated article of any of the preceding nine paragraphs, thecoated article may have a light-to-solar gain ratio (LSG) of at least1.22.

In the coated article of any of the preceding ten paragraphs, the coatedarticle may have a film side visible reflectance no greater than 8%,more preferably no greater than 5%.

In the coated article of any of the preceding eleven paragraphs, theglass substrate may be a clear glass substrate.

In the coated article of any of the preceding twelve paragraphs, thecoated article may have a glass side reflective a* value of from −8 to+1.0, and/or a film side reflective a* value of from −9 to +9.

Once given the above disclosure many other features, modifications andimprovements will become apparent to the skilled artisan. Such otherfeatures, modifications and improvements are therefore considered to bea part of this invention, the scope of which is to be determined by thefollowing claims:

What is claimed is:
 1. A coated article including a coating supported bya glass substrate, the coating comprising: a first infrared (IR)reflecting layer comprising ITO on the glass substrate; a firstdielectric layer comprising silicon nitride on the glass substrate overat least the first IR reflecting layer comprising ITO; a second layer IRreflecting layer comprising a nitride of titanium on the glass substrateover at least the first dielectric layer comprising silicon nitride, sothat the first dielectric layer comprising silicon nitride is locatedbetween at least the first IR reflecting layer comprising ITO and thesecond IR reflecting layer comprising the nitride of titanium; a seconddielectric layer comprising silicon nitride on the glass substrate overat least the second IR reflecting layer comprising the nitride oftitanium; wherein the coating contains no IR reflecting layer based onsilver; wherein the coating has a normal emittance (E_(n)) value of nogreater than 0.30; and wherein the coated article measuredmonolithically has: a visible transmission from about 15-80%, a filmside visible reflectance no greater than 10%, a glass side visiblereflectance no greater than about 30%, a glass side reflective a* valueof from −10.0 to +1.6, and a light-to-solar gain ratio (LSG) of at least1.10.
 2. The coated article of claim 1, wherein the coating containsonly two IR reflecting layers.
 3. The coated article of claim 1, whereinthe first dielectric layer comprising silicon nitride is located betweenand directly contacting the first and second IR reflecting layers. 4.The coated article of claim 1, wherein the second IR reflecting layercomprising the nitride of titanium comprises TiN_(x), where x is from0.8 to 1.2.
 5. The coated article of claim 1, wherein the second IRreflecting layer comprising the nitride of titanium comprises TiN_(x),where x is from 0.9 to 1.1.
 6. The coated article of claim 1, whereinthe second IR reflecting layer contains from 0-8% oxygen (atomic %). 7.The coated article of claim 1, wherein the second IR reflecting layercontains from 0-5% oxygen (atomic %).
 8. The coated article of claim 1,wherein the coating further comprises another dielectric layercomprising silicon nitride located between and contacting the glasssubstrate and the first IR reflecting layer.
 9. The coated article ofclaim 8, wherein the another dielectric layer comprising silicon nitridefurther comprises oxygen.
 10. The coated article of claim 1, where thesecond IR reflecting layer consists essentially of the nitride oftitanium.
 11. The coated article of claim 1, wherein the coating furthercomprises an overcoat comprising an oxide of zirconium.
 12. The coatedarticle of claim 1, wherein the coated article has a visibletransmission from about 20-70%, and a light-to-solar gain ratio (LSG) ofat least 1.15.
 13. The coated article of claim 1, wherein the coatedarticle has a light-to-solar gain ratio (LSG) of at least 1.22.
 14. Thecoated article of claim 1, wherein the coated article has a film sidevisible reflectance no greater than 8%.
 15. The coated article of claim1, wherein the coated article has a film side visible reflectance nogreater than 5%.
 16. The coated article of claim 1, wherein the glasssubstrate is a clear glass substrate.
 17. The coated article of claim 1,wherein the coated article has a glass side reflective a* value of from−8 to +1.0, and a film side reflective a* value of from −9 to +9. 18.The coated article of claim 1, wherein one or more of the dielectriclayers comprising silicon nitride further comprises oxygen and is dopedwith aluminum.
 19. The coated article of claim 1, wherein the coatedarticle is a monolithic window.
 20. The coated article of claim 1,wherein the coated article measured monolithically has an SHGC value ofno greater than 0.52.
 21. The coated article of claim 1, wherein thecoated article measured monolithically has an SHGC value of no greaterthan 0.45.
 22. The coated article of claim 1, wherein the first IRreflecting layer comprising ITO is from 100-1,000 Å thick, and thesecond IR reflecting layer comprising the nitride of titanium is from50-450 Å thick.
 23. The coated article of claim 1, wherein the first IRreflecting layer comprising ITO is from 250-450 Å thick, and the secondIR reflecting layer comprising the nitride of titanium is from 130-300 Åthick.
 24. A coated article including a coating supported by a glasssubstrate, the coating comprising: a first infrared (IR) reflectinglayer comprising ITO on the glass substrate; a first dielectric layercomprising silicon nitride on the glass substrate over at least thefirst IR reflecting layer comprising ITO; a second layer IR reflectinglayer comprising a nitride of titanium on the glass substrate over atleast the first dielectric layer comprising silicon nitride, so that thefirst dielectric layer comprising silicon nitride is located between atleast the first IR reflecting layer comprising ITO and the second IRreflecting layer comprising the nitride of titanium; a second dielectriclayer comprising silicon nitride on the glass substrate over at leastthe second IR reflecting layer comprising the nitride of titanium;wherein the coating contains no IR reflecting layer based on silver;wherein the coating has a normal emittance (E_(n)) value of no greaterthan 0.30; and wherein the coated article measured monolithically has avisible transmission from about 15-80% and a light-to-solar gain ratio(LSG) of at least 1.15.
 25. A coated article including a coatingsupported by a glass substrate, the coating comprising: a first infrared(IR) reflecting layer comprising ITO on the glass substrate; a firstdielectric layer on the glass substrate over and directly contacting thefirst IR reflecting layer comprising ITO; a second layer IR reflectinglayer comprising a metal nitride on the glass substrate over anddirectly contacting the first dielectric layer, so that the firstdielectric layer is located between and directly contacting the first IRreflecting layer comprising ITO and the second IR reflecting layercomprising the metal nitride; a second dielectric layer on the glasssubstrate over and directly contacting the second IR reflecting layercomprising the metal nitride; wherein the coating contains no IRreflecting layer based on silver; and wherein the coated article has avisible transmission from about 15-80%.
 26. The coated article of claim25, wherein the coating has a normal emittance (E_(n)) value of nogreater than 0.30.
 27. The coated article of claim 25, wherein the metalnitride is a nitride of titanium.
 28. The coated article of claim 25,wherein the first and/or second dielectric layer comprises siliconnitride.
 29. The coated article of claim 25, wherein the coated articlehas a film side visible reflectance no greater than 10%, a glass sidevisible reflectance no greater than about 30%, a glass side reflectivea* value of from −10.0 to +1.6, and a light-to-solar gain ratio (LSG) ofat least 1.10.
 30. A method of making a coated article including acoating supported by a glass substrate, the method comprising: sputterdepositing a first infrared (IR) reflecting layer comprising ITO on theglass substrate; sputter depositing a first dielectric layer comprisingsilicon nitride on the glass substrate over at least the first IRreflecting layer comprising ITO; sputter depositing a second layer IRreflecting layer comprising a nitride of titanium on the glass substrateover at least the first dielectric layer comprising silicon nitride, sothat the first dielectric layer comprising silicon nitride is locatedbetween at least the first IR reflecting layer comprising ITO and thesecond IR reflecting layer comprising the nitride of titanium; sputterdepositing a second dielectric layer comprising silicon nitride on theglass substrate over at least the first and second IR reflecting layers,so that the coating contains no IR reflecting layer based on silver, thecoating has a normal emittance (E_(n)) value of no greater than 0.30,and the coated article measured monolithically has: (i) a visibletransmission from about 15-80%, (ii) a film side visible reflectance nogreater than 10%, (iii) a glass side visible reflectance no greater thanabout 30%, (iv) a glass side reflective a* value of from −10.0 to +1.6,and (v) a light-to-solar gain ratio (LSG) of at least 1.10.